A catalytic mechanism investigation of TiF3 on hydriding/dehydriding properties of Mg85Cu5Ni10 alloy.

In this research, Mg85Cu5Ni10-x wt% TiF3 (x = 0, 2, 4, 6, 8) alloys were synthetized via ball milling and the catalytic mechanism of TiF3 on hydrogenation and dehydrogenation of Mg85Cu5Ni10 was studied. The microstructure, hydriding/dehydriding kinetics and thermodynamics of the alloys were discussed in detail. The TiF3 catalyzed alloys have faster hydriding/dehydriding kinetics and lower thermodynamic stability. After hydrogen absorption and desorption, TiF3 decomposes into TiH2 and MgF2. TiF3, TiH2 and MgF2 promote to forming crystal defects, dislocations, grain boundaries and nanocrystals which are advantageous to speeding up the rate of hydrogen absorption and desorption. The dehydrogenation activation energy E a(de) and dehydrogenation enthalpy ΔH(de) are reduced to 81.462 from 116.767 kJ mol-1 and 72.456 from 93.372 kJ mol-1 respectively by 6 wt% TiF3. An appropriate amount of TiF3 can improve the hydriding/dehydriding kinetics and thermodynamics of Mg85Cu5Ni10.